ARMED robbers fled with a security box full of money after ambushing a guard filling a cash machine.

The thieves struck at Asda, in Huyton, at 11.45am yesterday, just yards from the entrance used by hundreds of shoppers.

The men, who are thought to have been armed with knives, ran behind the G4S courier as he was heading to refill a Nationwide cash machine and took his security box, believed to contain thousands of pounds.

Within minutes, half a dozen police cars were on the scene but were too late to stop the thieves, who sped off in a getaway car. Dozens of shoppers watched officers seal off the crime scene, in Huyton Lane, using overturned trolleys to anchor their tape, and interview witnesses.

A Merseyside police spokesman said: “Up to three offenders were seen leaving the scene in a silver car having stolen a quantity of cash.

“The security guard was not injured but was left shaken by the incident.”

Police said they were not sure if a weapon was used, but G4S confirmed initial reports that a knife was used to threaten its couriers, part of a two-man team.

Business continued as usual at the store, which did not close its doors at any point during the day, although the robbery was the subject of much gossip inside.

An Asda spokesman said: “We contacted police as soon as it happened and the investigation is now in their hands.”

A similar incident occurred in Kirkby last month which saw a courier stabbed in the arm outside a bank.

Anyone who witnessed the incident and has not yet spoken to police is asked to call 0151-709 6010 or Crimestoppers anonymously on 0800 555111.